200 PLIOCENE MOLLUSCA. 



outer lip tliin, not expanded; inner lip forming a narrow and thin glaze u]ion the 

 pillar ; pillar but slightly flexuons ; canal open, turning to the left. 



Dimensions. — L. 36 mm. B. 18 mm. 



Distribution. — Not known living. 



Fossil : Butleyan Crag : Butley. 



Pliocene : Iceland. 



Bemarhs. — For some time I have had in my collection a Sipho-like shell from 

 Butley which I was unable to refer to any species known to me, either Recent or 

 fossil. Receiving a parcel of material, however, from the Iceland Crag from my 

 friend Dr. Pjetursson, I was interested to find in it a specimen evidently identical 

 with it, corresponding, moreover, with one described in the list and plates by 

 Mbrch and Poulsen as Buccinopsis elegans, Charlesworth, under the impression, no 

 doubt, that Wood's figure of Trophon (Afraefodon) elegans (Mon. Crag Moll., 1st 

 Suppl., tab. ii, fig. 6) was the same shell. In the Copenhagen list referred to, two 

 Iceland fossils are given as Buccinopsis elegans, Charlesworth, but neither of them 

 has, I consider, any relation to his genus Atractodon. One of them, together with 

 Wood's shell, has been identified by Dr. Dall as a Behring Sea species, Liomesus 

 canaliculatus (see p. 115 of the present memoir). The others, those now described, 

 should be referred, I believe, to Sipho, for though the canal in neither of them is 

 perfect, it is sufficiently so to show it is not that of Liomesus {Buccinopsis). Under 

 the circumstances I retain Morch's specific name of elegans for the present 

 specimens, again remarking that they are not Atractodon elegans, and changing 

 the generic name to Sipho. 



When the fossil and Recent forms, either of Neptunea or Sipho, are studied on a 

 large scale they often appear to run into one another, as do the Buccinums already 

 discussed, but probably this might be so with other groups of mollusca were it not 

 for the poverty of our collections and the imperfection of the geological record, the 

 difficulty of classification being in proportion to the amount of material at our 

 disposal. 



I cannot claim to have worked out, even provisionally, a Yevy complicated 

 problem, but have contented myself, as in a former case, with representing 

 typical specimens of the more characteristic forms known to me from the Crag' 

 giving them names, usually those at present to be found in the works of the 

 various authorities I have consulted, by which they may be identified. Whether 

 in some cases those names should be regarded as specific or varietal, and if varietal 

 to which of the already recognised species such varieties should be referred, I leave 

 to the judgment of my successors. I can only express the hope that the information 

 here given may prove of some value to those who may hereafter study the subject. 



